A belt type continuously variable transmission in which the rotation speed of an input shaft connected to a drive source is varied continuously and transmitted to an output shaft is known. A belt type continuously variable transmission is constituted by a primary pulley, a secondary pulley, and a belt wrapped around the pulleys, and by varying the width of each pulley, the contact radius between the belt and the pulley is varied, leading to variation in a speed ratio.
JP2004-183854A published by the Japan Patent Office describes a technique for performing this type of speed change control in which a map of speed change lines defining the relationship between vehicle speed, throttle opening, and input shaft rotation speed is stored in advance, and a target speed ratio is calculated on the basis of the driving conditions by referring to this map.